PHILADELPHIA, Pennsylvania (CNN) -- Four Philadelphia police officers will be fired, three others will be disciplined and a supervising sergeant will be demoted because of the violent beating of three suspects caught after a shooting, the city's mayor and police commissioner said Monday.

Policeidentified the three suspects as Dwayne Dyches, 24; Brian Hall, 23; and Pete Hopkins, 19. They have been charged with criminal conspiracy, aggravated and simple assault and reckless endangerment.

The suspects were believed to have been involved in a triple shooting at a streetcorner, Ramsey said. Of the 19 officers on the scene when the suspects were apprehended, eight had physical contact with the suspects, and a police review found only one of them to have acted within appropriate limits, he said.

Thirty-fifth District officers Vincent Strain, Patrick Gallagher, Patrick Whalen and Robert Donnelly are being dismissed for indiscriminate use of force, he said. Narcotics Strike Force officer Sean Bascom, 25th District officer Jonathon Czapor and 35th District officer Demetrios Pittaoulis are being suspended for from five to 15 days.

Although the supervising sergeant on the scene, Joseph Shiavone, did not have physical contact with the suspects, he is being demoted for his failure to intervene or subdue his subordinates.

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The district attorney's office and the FBI will continue their investigations of the incident, Ramsey said. He also said an outside group, the Police Executive Research Forum, has been contracted to further review the department's policies and procedures.

Lemoia Dyches, the mother of one of the suspects, said she was unable to see her son after his arrest. "They wouldn't even permit his attorney to see him," she said. "It strikes me as strange."

The police commissioner initially said officers had seen the suspects fire shots, injuring three people on a streetcorner. Three suspects fled the scene in a vehicle, and a fourth -- the shooter -- escaped on foot, Ramsey originally said.

However, media reports this weekend indicate police have changed their account; they now allege Hopkins was the shooter.

Deputy Commissioner Richard Ross, in charge of field operations, told The Philadelphia Inquirer there was confusion during the investigation over whether the gunman fled or returned to the vehicle.

"We certainly believe based on police witness accounts that four people drive up," Ross told the newspaper. "Then three people get back in the car and drive off."

The gunman got back in the car, Ross said. Police told the Inquirer they are still seeking a fourth suspect.

Ramsey said the police force has been under stress since Sgt. Stephen Liczbinski was shot and killed with an assault rifle May 3 while responding to a bank robbery. One suspect in that shooting was killed by police in the confrontation, and another has been apprehended. A third suspect is at large.

Authorities want to know whether the officers' emotions over Liczbinski's death -- and their desire to apprehend the suspect who remains at large -- had a role in their actions.

Stress levels among officers on the street are "simply too high," and the department aims to eliminate 12-hour shifts, Ramsey said soon after the incident.